Hi I think you want to read captcha image If thats your requirement
you have a plugin for captcha integration
From your application root, you can run:
ruby script\plugin install svn://rubyforge.org/var/svn/expressica/plugins/simple_captcha
In Your Code:
To show a captcha in your view, just use the following tag:
<%= show_simple_captcha %>
In your controller to validate:
if simple_captcha_valid? end